Our objectives are to a) elucidate the biological prerequisites for periodontal tissue regeneration adjacent to artificial root surfaces, b) develop optional clinical methods for the treatment of root perforations and root canals in situations where a retrograde approach is needed and c) contribute to the development of clinical methods aiming at regeneration of lost periodontal tissue support. The specific aims are 1) to develop an experimental model for studying the wound healing events adjacent to artificial root surface areas; 2) to study the possibility of obtaining periodontal tissue regeneration, i.e. production of new connective tissue attachment with cementum formation, on an artificial root surface facing a wounded periodontal area; 3) to compare the capacity of periodontal tissue regeneration (described under point 2) adjacent to different materials constituting the artificial root surface (titanium oxide, silicone and guttapercha) with that of a cavity-prepared or scaled natural root surface; 4) to compare the capacity of the periodontal ligament tissue to regenerate adjacent to artificial root surfaces in different animal species (dogs and monkeys). The experimental plan comprises a surgical approach to the buccal surfaces of the teeth of dogs and monkeys. Circular fenestrations are created through the buccal bone plate at different levels and well defined cavities are prepared in the root surface. These cavities are then obturated with test material (silicone, titanium coated silicone and guttapercha) which are compared with empty preparations or scaled surfaces with regard to regeneration of the various periodontal tissue components including formation of new cementum. The healing events will be quantitatively characterized histometrically as well as morphometrically.